1. Field of the Invention
The present invention generally relates to detecting defects on a wafer using template image matching.
2. Description of the Related Art
The following description and examples are not admitted to be prior art by virtue of their inclusion in this section.
Inspection processes are used at various steps during a semiconductor manufacturing process to detect defects on wafers to promote higher yield in the manufacturing process and thus higher profits. Inspection has always been an important part of fabricating semiconductor devices. However, as the dimensions of semiconductor devices decrease, inspection becomes even more important to the successful manufacture of acceptable semiconductor devices because smaller defects can cause the devices to fail.
Inspection generally involves applying some defect detection parameters to output generated by scanning and/or imaging a wafer. The defect detection parameters may include a threshold that is applied to the output or to a difference between the output and some reference output. Different detection thresholds can be set depending on varying characteristics of the output such as brightness and/or noise due to roughness of different regions of a device, but typically not depending on the locations of the regions within the inspected area. There is no easy way to treat different regions in the output separately according to the device context resolved in the output.
Information beyond simple defect detection is often generated during inspection processes. For example, the detected defects are often classified into different groups. In one such example, after finding defects, they may be classified into different groups based on the defect characteristics such as size, magnitude, and location. Defects can also be classified based on the information contained within a patch image, a relatively small subsection of the full image. Sometimes, the context in which a defect was found cannot be determined from a patch image alone, requiring a larger section of the image surrounding the defect.
Accordingly, it would be advantageous to develop methods and systems for detecting defects on a wafer that do not have one or more of the disadvantages described above.